


Children Of Darkness

by E_Bel



Category: Undertale (Video Game)
Genre: De-aging, M/M, Nightmare has a soft side, Nightmare will defend his children to the death, being volunteered for things that you very much did not want to do, but its there, good dad Nightmare, is on the list of terrible no good very bad ideas, its very rare and exclusively for a select few, life knows what she's doing, of the lord of negativity, or rather your death, reaper does not, reaper has a crush, rip swap!papyrus, turns out trying to take away the children
Language: English
Status: Completed
Published: 2018-12-09
Updated: 2018-12-09
Packaged: 2019-09-14 14:57:54
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,105
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16915044
Author URL: https://archiveofourown.org/users/E_Bel/pseuds/E_Bel
Summary: Reaper initially thought that he got the short end of the stick; while everyone else got to panic in comfort, he got shipped off with a highly-volatile Nightmare and the newly de-aged evil Sans crew to Life's place to see what help she could bring. He didn't imagine he'd find himself smitten with the lord of darkness, not in a million years. Who knew Nightmare had a sweet side?





	Children Of Darkness

**Author's Note:**

> Credit to official-arubaocean from Tumblr for the title, I couldn't think of anything myself.

If someone had told Reaper, even just a day ago, that he would be stuck doing a babysitting gig for small children with the king of negativity himself, he’d have probably laughed in their face and then recommended them to a professional. Beyond the fact that Reaper should never be in charge of looking after younglings (He kills things by touching them, babies/young children require a lot of physical touch; hopefully, everyone can see the problem here), the idea that Nightmare would be anything remotely approaching a good caretaker for children was frankly absurd. And yet, here he was; Poking his tongue out and in rapidly like a froggit in an attempt to keep a tiny Cross (who was currently about two decades younger than he was supposed to be) from bursting out into great streams of tears again, whilst the lord of darkness himself bounced the little chub bub in his arms and his tentacles worked at lightning speed doing…something, Reaper couldn’t really see what. At least the other four kids had stopped crying. 

Reaper counted it as a victory when Cross gave a little hiccupped-laugh and dared to look over at the remains of the bad sans group for a moment. Whatever that liquid was that Sci had made, it was certainly potent. Error was the oldest, somewhere between three and four, and also the quietest; the kid had found a baby blanket shortly after Reaper had packed the children and their overprotective not-father to Life’s house, and had taken to carrying the thing everywhere with him. Next was Killer, at a bratty two to three years, stacking blocks as high as he could. Then came Horror and Dust, both somewhere in between one and two years of age and loud in the way that only young kids could be; at least it seemed that all were playing nice. Finally, there was Cross; Reaper looked back to the tiny babybones. The youngest of the group wasn’t even a year old by Life’s estimates, and was still in a deep state of distress from a stranger attempting to steal him away from his family.

Reaper felt a shiver go down his spine at the memory. Of course, Stretch had done so with the best of intentions; intending to take the kids away from someone everyone thought would never be able to care for them properly and give them to someone who could but the kids, and especially not Nightmare, didn’t see it that way. Reaper remembered the lights bursting from the amount of negative energy that Nightmare began emitting the second Cross began screaming and crying from Stretch’s arms, plunging the room into darkness. Everyone was frozen with terror as they were bombarded with the feeling of a fate so horrible that they would be begging for death; Stretch was beaten to a bloody pulp by Nightmare’s tentacles, after they’d removed Cross from him, while Sci was huddled in the foetal position screaming that ‘he was next, he was next, oh stars, he was going to DIE’. It was a relief for everyone when Dream finally showed up and took charge, even if that charge involved packing his vicious and trigger-happy brother off with Reaper to go see what aid Life could give. But, he supposed, it wasn’t too bad; Nightmare had calmed down a lot once Reaper had gotten him away and focused on the children more than on him.

Reaper was broken out of his musings when he caught the scent of melting cheese and looked over the shoulder of Nightmare which didn’t have a baby on it to see what the goop skeleton was doing. There was a pot on the stove and a smaller one off the stove with a baby’s bottle warming in it, Nightmare’s tentacles working in pairs on each. Cross let out a soft noise and the skeleton’s attention turned from the food to the baby, murmuring soft replies with a gentle smile and drawing a giggle from the babybones. It almost seemed like the King had forgotten he was here and, just for an instant, Reaper felt like he’d gotten a glimpse into a forbidden world; a side of Nightmare that he was not allowed to see. The softness and gentleness were completely at odds with the menace that Reaper had thought he’d known. Just for a moment, Reaper could see the person that Dream said he’d once known and it transfixed him; he dared not look away, just in case it was gone by the time he looked back.

“If that is lunch for us and the young ones, then it’s just in time.” And, in an instant, the moment shattered. The instant Life began to speak, Reaper watched as Nightmare remembered where he was and who was with him, and the soft side of Nightmare quickly slide back into hiding under layers of cold indifference. It hurt more than Reaper thought it would, watching it go away. Reaper turned to the door of the kitchen as Life entered, her entire focus on Nightmare and his on her. “I have some results.”

 

* * *

 

“It seems that, whatever Sci made, it de-aged all those who touched it by about twenty-two years.” Reaper admired how easily Life kept her calm with a baby Horror snapping playfully at her fingers each time she tied to bring spoon close to him. Dust was proving easier to feed, happily eating his mac&cheese without trying to take chunks of his fingers off. Admittedly, that would have been hard for the little bub with the thick, long gloves Reaper was currently sporting to protect the kids but it was better that he didn’t try.

“Which would explain why Killer is old enough for a sippy-cup while Cross still has to be fed from a bottle.” Nightmare, as the only one that Cross allowed to pick him up, was feeding the youngest of the crew himself. Error was old enough to handle a spoon himself with a tentacle to occasionally help him, while the other three were trying to contain the cheesy mess that Killer was making; it seems he’d grown bored of eating.

“I would have thought that Error would have been older than twenty-five.” Reaper mused, his eyes wandering over the other black-boned skeleton.

“He is,” Nightmare commented, nonchalantly dodging a blob of cheese that Killer had tossed. “From what I could see, the potion interfered badly with his glitching. From what I felt, everyone else de-aged with one burst of magic. Error had at least five bursts that I sensed before I was distracted by my own.” Reaper looked at Nightmare oddly when he heard this.

“You don’t look like you were affected by the liquid.” The king of negativity rolled his eyes in response and levelled an un-amused glare at him.

“That’s because there is very little difference between my five-hundred-and-two-year-old self and my four-hundred-and-eighty-year-old self. My long lifespan means the effects were not as devastating to me as it was to others, but rest assured, I am twenty-two years younger than I should be.” Reaper shrunk in on himself a little and quickly turned back to feeding Dust.

“Then I will focus on Error’s sample first. It seems like whatever it was has finished doing what it wanted to do, but Error’s bad reaction worries me. It might still cause him problems.” Life managed another fabulous dodge before depositing the final spoonful in Horror’s mouth. The kid swallowed, then let out a great yawn. “It appears that these little ones are ready for a nap. I have spare rooms, beds, and cribs if you would like.”

“That would be much appreciated.” Nightmare’s attention was mostly on Killer, who was now squirming in his highchair to try and avoid the wipes the tentacles were now wielding, but he did sound genuinely grateful. “I’ll take care of that myself if you could start researching as soon as possible?” Life nodded with a smile, clapping her hands happily.

“And that means Reaper can clean the kitchen.” Reaper’s eyes quickly darted to her in a panic, catching sight of the cheese disaster zone the kitchen had become during feeding time along the way.

“That means Reaper can what?”

 

* * *

 

Reaper dragged himself up the stairs, kitchen finally clean, looking for a spare bed. He hoped there was at least one still free that wasn’t claimed by a kid, he could use a nap himself. The first room he came across was no dice; A child’s bed sat in one half with Error snoozing away, still clutching his blanket, and the other half had a baby’s crib with Cross tucked inside. Reaper closed the door gently, not wanting to wake the two kids. The next room wasn’t any better, with two cribs for Dust and Horror; though the kids preferred to be babbling sleepily to each other rather than napping. It was as he was making his way to the third room that he heard something.

“No Daddy! No nap!” It wasn’t loud, but it was clear that was because of distance rather than any effort on the speaker’s part to be quiet. He glanced down the hallway to see an open door and curiosity compelled him to go investigate. He quietly crept up on the door, the childish shouting continuing as he moved forward. He peeked inside to see mini-Killer throwing a massive tantrum, crying that he didn’t need a nap, and Nightmare trying to soothe the kid.

“Killer, you need to take a nap.” The kid was having none of it, kicking his feet out wildly and knocking himself onto his back on the bed.

“No Daddy! No nap!” It could barely register to Reaper that the child was actually calling Nightmare 'Daddy’ as he watched, fascinated. He watched Nightmare heave a sigh.

“How about a story first? If we read a book together first, will you then try to sleep?” Something in Nightmare’s words seemed to catch Killer’s attention as he soon stopped flailing and sat up with big eyes aimed at Nightmare; speaking of, who knew that Killer had blue eye-lights?

“Story?” Nightmare nodded, pulling a book from the shelf that Reaper recognised all too well from his trips around the multiverse, Fluffy Bunny. He almost gave himself away at the sight of Nightmare’s face once the king realised what he’d picked from the shelf, but it was too late to put it back; Killer had zeroed in on the cover and was now making grabby hands towards it. So the king of negativity begrudgingly brought the book over to Killer. Picking up the small child, Nightmare settled the two of them on the bed, Killer resting on his chest and supported by one arm while the other held the book in front of both of them.

Again, Reaper was struck with the feeling that he was observing something through the looking glass. Slowly, hesitantly, the soft creature that wore Nightmare’s face reappeared; a being that cuddled his child without hesitation, and read them stories. Reaper stood steadfast to his spot, practically hypnotised, as he watched Nightmare read the entire story to an ever-tiring Killer, and obeying the child when asked “Again”. He was not meant to be here, this was not his to see, and yet he couldn’t bring himself to leave; some part of him wanted him to remember as much of this as possible, to burn it into his skull so he’d never forget it. And when first Killer, then Nightmare himself drifted off into sleep, he found himself entering the room. Without really knowing what he was doing, he found a spare blanket and laid it over the black skeleton before leaving, shutting the door gently behind him so they wouldn’t be disturbed.

He felt disconnected from his body, standing there in the hallway. He’d seen something he was never truly meant to see, and he couldn’t decide if it changed everything or nothing. That hesitant, but very real, smile he now knew Nightmare possessed, to be shown only to a very exclusive few; A tiny hint of softness that was hidden away from the world. Reaper could still see it when he closed his eyes. 'I want that smile shown freely to me,’ He suddenly realised. It took him a few moments to process his epiphany before he hurried to a window, shaken by his realisation. A glance at his reflection confirmed his fears; both his cheeks had blue magic swirling beneath them, lighting his face up. He let out a whine and buried his face in his hands; he was so screwed.


End file.
